9.3.2 An example pinboard object

To create your own pinboard objects, the class drawn-pinboard-object is provided, which is a pinboard-object that accepts a display-callback to display itself. The following example uses this class to create a new class of pinboard-object that displays an ellipse.

(defun draw-ellipse-pane (gp pane

                          x y

                          width height)

  (with-geometry pane

    (let ((x-radius

           (floor %width% 2))

          (y-radius

           (floor %height% 2)))

      (gp:draw-ellipse

       gp

       (+ %x% x-radius)

       (+ %y% y-radius)

       x-radius y-radius))))

(defclass ellipse-pane

     (drawn-pinboard-object)

  ()

  (:default-initargs

   :display-callback 'draw-ellipse-pane

   :visible-min-width 50

   :visible-min-height 50))

(contain

 (make-instance 'ellipse-pane))

Figure 9.7 An ellipse-pane class

The with-geometry macro is used to set the size and position, or geometry, of the ellipse drawn by the draw-ellipse-pane function. See the LispWorks CAPI Reference Manual for more details.

Now that you have a new ellipse-pane class, you can create instances of them and place them inside layouts. For instance, the example below creates nine ellipse panes and place them in a three by three grid.

(contain

 (make-instance

  'grid-layout

  :description

  (loop for i below 9

        collect

        (make-instance 'ellipse-pane))

  :columns 3))

Figure 9.8 Nine ellipse-pane classes in a layout